Human Touch: Sensor Lets Robots 'Feel'

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Robots do not look human just yet, but soon they may get the
"human touch." Researchers say they have developed a flexible
sensor able to detect temperature, pressure and humidity
simultaneously, and more accurately than currently existing
devices.

In addition to improving robotics, the sensor could one day be
embedded into the "electronic skin" of prosthetics, to
help amputees sense environmental changes.

The sensor is "a huge step towards imitating the sensing
features of the human skin," said study author Hossam Haick,
a professor of chemical engineering and nanotechnology at the
Technion-Israel Institute of Technology in Haifa. The device is
about 10 times closer to how real human skin senses the
environment, compared with other designs.

To make the device, the researchers integrated
gold nanoparticles covered with organic connector molecules,
called ligands, into the surface of a plastic commonly used to
make water bottles. The system has a flowerlike arrangement, with
a layer of gold in the center, and the ligands forming the
"petals."

When the plastic is bent or pressed upon, the nanoparticles
inside shift, and the distances between them change. This shift
affects how quickly electrons can pass between the particles,
altering the electrical characteristics of the sensor. [ Bionic
Humans: Top 10 Technologies ]

In other words, a change in pressure affects how well the
compound conducts electricity. "By measuring the electrical
resistance, we can know how much pressure was applied on the
sensor," Haick said.

Temperature and humidity also affect the distance between the
nanoparticles in a similar way, he added. "By using a combination
of software and hardware operations, it is possible to isolate
the values for humidity, temperature and touch — making the
sensor 3-in-1."

The researchers also found that by altering the thickness and
material of the plastic surface, they could control the
sensitivity of the sensor.

Changing the properties of the plastic "allows measuring a large
range of loads, ranging from tens of milligrams to tens of
grams," Haick said.

This means that in addition to being used in prosthetics and
giving a
humanlike "sense of touch" to robots, the sensor could be
used in an early warning system to detect abnormal temperatures
and tiny cracks in airplanes, bridges and other structures.
Another possible application could be to monitor people's health.

Of course, to function as a real artificial skin, the signals
received by a tactile prosthetic limb would have to be
transmitted to the brain. To do so, the sensor would have to be
connected to the human nervous system, and the technology for
such a connection does not exist.

"Until complete implementation of this vision, an intermediate
development would be the integration of e-skin with a computer
system," Haick said.

The study is detailed in the June issue of the journal Applied
Materials & Interfaces.